mysql - Json decode string not working on php -

it working on 1 day see below json decode not working.

<?php  $data = $_post["data"];  $jsonstring= urldecode(stripslashes($data));  $input = json_decode($jsonstring, true);  $myfile = "testfile.txt"; $fh = fopen($myfile, 'w') or die("can't open file");  fwrite($fh, $input);   fclose($fh) 

i have checked value of $data , $jsonstring having vaild json string. string $input empty.any suggestion...?

please check , error number , post it

echo json_encode($jsonstring, true); echo json_last_error_msg();  function json_last_error_msg() { static $errors = array(     json_error_none             => null,     json_error_depth            => 'maximum stack depth exceeded',     json_error_state_mismatch   => 'underflow or modes mismatch',     json_error_ctrl_char        => 'unexpected control character found',     json_error_syntax           => 'syntax error, malformed json',     json_error_utf8             => 'malformed utf-8 characters, possibly incorrectly encoded' ); $error = json_last_error(); return array_key_exists($error, $errors) ? $errors[$error] : "unknown error ({$error})"; 

}